In general, an electric vehicle, which is equipped with only an electric motor as a driving source, emits a significantly low traveling sound when traveling at a low speed. Similarly, a hybrid vehicle, which is equipped with an electric motor and an internal combustion engine as driving sources, also emits a significantly low traveling sound when traveling at a low speed only with driving power of the electric motor. Accordingly, a pedestrian or other person may not notice proximity of such a vehicle.
In consideration of this, for example, JP-A-5-213112 discloses a vehicle proximity annunciator device equipped in such a low noise vehicle. The vehicle proximity annunciator device causes a sound emission device such as a speaker or a piezoelectric buzzer to emit an annunciation sound to the outside of the vehicle thereby to notify a pedestrian and the like around the vehicle of existence of the vehicle.
In another example, a vehicle proximity annunciator device is configured to emit a dummy engine sound or a dummy motor sound by generating an annunciation sound being a synthetic sound (chord sound) including multiple frequency components. In another example, a vehicle proximity annunciator device is configured to change the pitch (playback speed) of the annunciation sound according to the vehicle speed to enable a pedestrian and the like to recognize the speed of the vehicle.
It is noted that, such a configuration may be employed to cause a sound emission device to emit a synthetic sound as the annunciation sound and to change the pitch of the annunciation sound according to the vehicle speed, as described above. Nevertheless, in such a configuration, the sound pressure of specific frequency components of the synthetic sound may increase, and the sound pressure of other frequency components of the synthetic sound may decrease, with change in the vehicle speed, due to influence of the frequency characteristic of the sound emission device.
Therefore, the sound pressure of the annunciation sound may become higher or may become lower with increase in the vehicle speed. Alternatively, the sound pressure of the annunciation sound may sharply change with change in the vehicle speed. Consequently, a pedestrian and the like cannot notice proximity of the vehicle easily or may feel the annunciation sound as a noise.